1. Field of the Invention
The present invention relates to virtual reality presentation devices for providing experience of virtual three-dimensional (3D) spaces and to information processing methods.
2. Description of the Related Art
Virtual reality (VR) presentation devices have been available. A virtual reality presentation device includes, for example, an image display, such as a head mounted display (HMD), position and orientation detection means, such as a position and orientation sensor, for detecting the position and orientation of a viewpoint of an observer, and computer graphics (CG) image generation means.
For example, a magnetic position and orientation sensor is used as the position and orientation detection means. The magnetic position and orientation sensor is installed in the HMD worn by the observer so that the position and orientation of the head of the observer are detected. Magnetic position and orientation sensors detect the relative position and orientation between a magnetic source (transmitter) and a magnetic sensor (receiver). For example, FASTRAK®, which is a product of Polhemus, is available as a magnetic position and orientation sensor. FASTRAK® is a device for detecting a three-dimensional position (X, Y, and Z) and an orientation (pitch, yaw, and roll) within a predetermined range in real time.
The CG image generation means places a 3D modeled CG image in a virtual space having the same scale as the real space, and renders the virtual space from the position and orientation of the viewpoint of the observer detected by the position and orientation detection means.
Displaying the CG image generated as described above on the image display, such as the HMD, allows the observer to feel as if he or she is immersed in the virtual CG space.
In the above-mentioned system, in order to move a position within a virtual space, an observer actually must move the position. The position of equipment must be moved, and a real space having the same size as the virtual space is required. Thus, position movement instruction means for separately instructing position movement has been provided. For example, a direction is designated using the position and orientation sensor and position movement in that direction is instructed by pressing a button separately provided, or position movement is instructed using a device, such as a joystick. Moving a position freely within a virtual 3D space and performing observation is called “walkthrough”. In this case, a rendering viewpoint of a CG image changes depending on the position and orientation of the viewpoint of the observer. Thus, if the position and orientation of the viewpoint changes in a moved position, a virtual space can be observed from that viewpoint.
In addition, in recent years, technologies for presenting to users information that does not exist in the real world by combining 3D CG images and images in the real world have been developed. Such technologies are called augmented reality (AR) systems or mixed reality (MR) systems described, for example, in U.S. Pat. No. 6,522,312.
MR systems are capable of superimposing 3D CG images on real objects. U.S. Pat. No. 6,522,312 proposes a system allowing users to freely control a virtual object by superimposing the virtual object on a real object.
In known systems, when an observer is immersed in a virtual 3D space and keeps moving an observing position within the virtual 3D space, it is difficult for the observer to know a position at which the observer is located in the virtual 3D space.